1. Field of the Invention
This invention relates to ventilating systems utilizing hoods for removing grease and smoke from the spaces above cooking surfaces, particularly in restaurants.
2. Description of the Prior Art
There has been much activity in the field of ventilating systems and particularly in the field of hoods for filtering grease and smoke in restaurants in the past several years. Most of the prior art systems have utilized blowers for both the exhaust and the inlet. However, due to the fact that air is introduced from the outside, it has been necessary in most instances to preheat the incoming air so as not to unduly lower the temperature of the restaurant. Thus, for example, with most ventilating hood systems used in restaurants the prior art has utilized a so called perimeter supply plenum so that a laminar flow of air is introduced around the perimeter of the hood. In some instances, the laminar flow of air is only in the front of the hood, which nevertheless, creates some discomfort for the cook standing directly below the flow of frigid air from the outside. Thus, it has been necessary in most instances to pretemper the cold air coming into the entrainment chamber defined by the hood. One approach to lower the heating bill for restaurants has been proposed by Lester H. Brown in U.S. Patent 3,800,689. Brown proposes a by-pass duct extending from the exhaust blower outlet to the intake blower inlet and a damper responsive to temperatures sensed in the intake duct to pretemper the inlet air. Kuechler in U.S. Pat. Nos., 3,943,836 and 3,952,640 proposed a liner for the hood which was substantially curved to produce a vortex action within the entrainment chamber and which directed the inlet air and gas fumes from the cooking surface directly into the filter media and out through the exhaust. Many other proposals have been made but all have dictated the use of an intake plenum and in many cases even accessory heating elements for heating the intake air.